Groundsmaster 52 runs 10 minutes, then dies

[Volvoman]

Volvoman, I just fixed a briggs motor that was doing the same thing. Some briggs motors have a spring loaded fuel shut off valve that shuts off the fuel when you shut the key off to keep it from backfiring when you turn the key off. It is a round insert that goes directly into the carb. there is a spring loaded needle valve inside that has a wire lead to it. if that wire breaks or the 12 volt is interrupted ti will shut off most of the fuel. My teck expert told me to unscrew the valve housing and cut the needle off. That saved me $50 for a replacement.

Sounds like something on a later Briggs. My Groundsmaster 52 was made in 1980, when flathead (L-head) engines were the norm for lawn mowers and garden tractors. Was the engine you just fixed an OHV engine?

 

[Tony H]

I know you went to lengths to be thorough with the carb. Just wondering if the jets (emulsifier tube)still have some restrictions. Enough varnish to decrease the diameter a bit.
Look at picture #5. If air vent to bowl is clogged, bowl can't get fuel.

https://outdoorpowerinfo.com/repairs/briggs_small_two-piece_flo-jet_part2.asp

 

[lacritz]

I have a problem with a old Craftmans tow behind grass vacuum. Just sucks up the grass clippings from the riding mower. I found that inside the carburator there is a neddle valve that gets clogged with dirt, starving the engine of gas. I had to remove the neddle valve and clean all the dirt and gunk out. Runs fine after the cleaning, or maybe get a replacement carb?

 

[MossRoad]

In your current situation, gas with ethanol causing your current problems is a red herring. You’ve drained the tank and flushed the fuel system with fresh gas.

 

[Volvoman]

In your current situation, gas with ethanol causing your current problems is a red herring. You’ve drained the tank and flushed the fuel system with fresh gas.

Yes, the problem now exists with fresh non-oxygenated gasoline. If I was a betting person, I would place my money on the problem being inside the carburetor somewhere. I have considerable experience with Kohler engine carbs, but not much with those used by Briggs. So, I can’t say one way or another which tend to be more finicky. This carb has been performing very well for over 40 years, so I can’t say it isn’t a quality carb. But, I do know that over the past 40 years fuel quality is definitely different than it was back in 1980, and carbs tend to accumulate varnish deposits far more quickly than before, thereby causing more fuel related issues now than before.

 

[laurencen]

had a similar issue on a forklift, ran great for a short period and died, fuel bowel empty so installed a electric pump, similar issue so I emptied the tank, used a shopvac with a 3/4 plastic hose to vacuum the tank bottom, lots of junk and refilled, to my surprise same issue, turned out the pickup tube had a bug or seed in it, idle it was sitting there but full rpm it sucked up the tube and stuck at the 90 elbow starving gas, shut down it sank to the bottom of tube

check the pickup line

 

[Volvoman]

had a similar issue on a forklift, ran great for a short period and died, fuel bowel empty so installed a electric pump, similar issue so I emptied the tank, used a shopvac with a 3/4 plastic hose to vacuum the tank bottom, lots of junk and refilled, to my surprise same issue, turned out the pickup tube had a bug or seed in it, idle it was sitting there but full rpm it sucked up the tube and stuck at the 90 elbow starving gas, shut down it sank to the bottom of tube

check the pickup line

By “pickup” line, are you referring to the line from the tank to the fuel filter, or the line between the filter and the carburetor? I have already replaced them both with new on the GM after flushing out the tank with a high pressure washer for several minutes. As for the bug…it served as a floating check valve, something that I had suspected was occurring in the GM’s system too, but after replacing the lines and cleaning the carb, I am 99% sure there isn’t anything like that going on here. It IS what happened to me in the past once, on the old Studie that Ii described above.

 

[jaxs]

I believe you are on the right path in ordering the OEM carb rebuild kit but while waiting for it,you might clear up a couple of things. Seafoam doesn't make smoke, especially in maintenance dose of 2-3 oz per gallon. The blue smoke coupled with finding out there's a pulse fuel pump involved points to a possible problem. Oil can leak through a pinhole of failing diaphragm. "IF" diaphragm has a pinhole that would cause fuel starvation "AND" account for blue smoke. I believe you are aware of this but a word of caution anyhow. If fuel pump is the problem,odds are there's gas in the crankcase so keep that in mind or you might have to use that last overbore sooner than expected. One way of testing this theory is disconnect pulse hose,connect a temporary fuel tank that is higher than carb and watch for fuel drip from where pulse hose connects to pump. Dripping gas makes it a certainty of failed pump diaphragm. If there's no drip,start engine to see if it still boggs when deck is engaged.
I'm not suggesting a problem with condenser but want to say something about condensers in general. IMO condensers are one of the most difficult problems to nail down. NEVER throw old condensers away,have them professionally tested then label and save for future use. Everyone complains about quality of products manufactured today and condensers are at the top of the list. It isn't uncommon to have an engine run poorly,not start or intermittently run rough after a routine tune up,becasue new condenser is bad.

 

[laurencen]

my recommendation when it dies open the drain on the carb bowl, is it empty or full? those impulse pumps are not great with age and the ethanol gas, pick up a cheapo electric and try it again, had a issue with a mule where the float shutoff pin the center should be spring loaded but it was stuck in the out position, freeing the pin corrected the low fuel level in the bowl

on my machines I have switched to the electric pumps, way easier to check

 

[Richard001]

If the fuel pump is like what Rotax uses on some engines it is a diaphragm with fuel on one side and engine vacuum pulses on the other side. In the case of Rotax, the pulse line is connected to the crankcase and the piston moving up and down causes the pulsing which causes the diaphragm to move back and forth. A couple of reed valves on the fuel side cause it to be pumped through to the carb. The issue with having the pump above the crankcase fitting is to make sure any splashed oil drains back into the engine and out of the pump. If the pump gets swamped with oil it will reduce or completely cut off the ability of the diaphragm to move. Rotax solved this problem by drilling a little tiny weep hole in the housing on the vacuum side of the diaphragm with instructions to make sure the pump is mounted with the hole pointed down. Any accumulated oil or condensation will drain out the weep hole.

That is a mower and engine worth preserving. Good luck with your issue.

Great post. However this only works if the pulse line does not have a loop that can cause oil to collect in the pulse line. The pulse line must NOT have a loop between the pump and the pulse port. In other words, the pulse line MUST be all down hill from the pump.